Fiber optic communication is an emerging method of transmitting information from a source (transmitter) to a destination (receiver) using optical fibers as the communication channel. A Wavelength-Division Multiplexing Passive Optical Network (WDM-PON) is an optical technology for access and backhaul networks. WDM-PON uses multiple different wavelengths over a physical point-to-multipoint fiber infrastructure that contains passive optical components. The use of different wavelengths allows for traffic separation within the same physical fiber. The result is a network that provides logical point-to-point connections over a physical point-to-multipoint network topology. WDM-PON allows operators to deliver high bandwidth to multiple endpoints over long distances. A PON generally includes an optical line terminal located at a service provider central office (e.g., a hub), a remote node connected to the central office by a feeder fiber, and a number of optical network units or optical network terminals, near end users. The remote node demultiplexes an optical signal from the central office and distributes the demultiplexed optical signals to multiple optical network units (ONUs) along corresponding distribution fibers.
Generally, the more wavelengths that can be stacked by the WDM-PON, the more information that can be carried by a single distribution fiber to lower infrastructure construction and management costs of the WDM-PON. Wavelength tuning of a tunable laser in the ONU for generating the upstream optical signal is generally carried out by adjusting an injection current applied to the tunable laser. Temperature control through a Thermoelectric Cooler (TEC) circuit may additionally fine-tune the wavelength of the tunable laser. Extending the wavelength tuning range, however, is strongly dependent upon fabrication technology employed by the tunable laser. Accordingly, a tunable laser will typically undergo a costly re-fabrication to extend the wavelength tuning range in order to provide additional wavelengths to meet increases in the amount of data being transmitted over the WDM-PON.